The present invention relates to methods for forming dovetails on turbine buckets for connection with turbine wheels and particularly relates to electrodischarge machining methods for forming arcuate dovetail configurations along opposite sides of recesses of turbine bucket dovetail preforms, enabling the buckets for securement on correspondingly-shaped wheels of a turbine.
Presently, dovetails are formed on turbine buckets, typically in a casting process or by milling. For example, a three-bar linkage path generator with a single flute end-mill may be used to machine the dovetail to its final dimension. Alternatively, a three-axis CNC milling machine with a rotary table setup may be utilized. Both processes are labor-intensive, require significant operator interaction, and are time-consuming and tedious. In providing turbine buckets, however, the quantity of buckets required and the uniqueness or the style of the buckets ordered dictates a need for a stable predictable process for forming the dovetails. The resulting surface finish and tolerances produced with the current dovetail milling processes are not repeatable or predictable. Accordingly, there is a need for an accurately repeatable predictable process for forming dovetails in turbine buckets in a more efficient manner, with elimination of many of the current tooling preparation steps, as well as reduction in operator interaction and material consumption and scrap, together with increased automation and productivity.